Can I run the single power from 3-wire 220 cord to both power receptacles in a hot tub panel made for 4-wire?
You should call a qualified professional electrician who has done hot tubs and spas. This is not a DIY project. There are several very fine points about a hot tub installation that if done wrong or not 100% correct can prove dangerous or fatal to any users of the hot tub. There is just too many chances for one little mistake to cause a very serious injury. it is not worth the risk.
